Why does my Two factor authentication can't be turn off?

From the article below. If it has been on longer than 2 weeks, you can't turn it off. There has been some posts that state the article is no longer correct and now you can't turn it off, but I haven’t been able to verify that.

Can I turn off two-factor authentication after I’ve turned it on?

If you already use two-factor authentication, you can no longer turn it off. Certain features in the latest versions of iOS and macOS require this extra level of security, which is designed to protect your information. If you recently updated your account, however, you can unenroll for a period of two weeks. Just open your enrollment confirmation email and click the link to return to your previous security settings. Keep in mind, this makes your account less secure and means that you can't use features that require a higher level of security.

Apple ID -Two-factor authentication

That's right. You had a two-week window to turn it off when you first set it up, so now it's permanent.